Effects of Tylosin Use on Erythromycin Resistance in Enterococci Isolated from Swine

Abstract

The effect of tylosin on erythromycin-resistant enterococci was examined on three farms; farm A used tylosin for growth promotion, farm B used tylosin for treatment of disease, and farm C did not use tylosin for either growth promotion or disease treatment. A total of 1,187 enterococci were isolated from gestation, farrowing, suckling, nursery, and finishing swine from the farms. From a subset of those isolates (n ‫؍‬ 662), 59% (124 out of 208), 28% (80 out of 281), and 2% (4 out of 170) were resistant to erythromycin (MIC > 8 g/ml) from farms A, B, and C, respectively. PCR analysis and Southern blotting revealed that 95% (65 out of 68) of isolates chosen from all three farms for further study were positive for ermB, but all were negative for ermA and ermC. By using Southern blotting, ermB was localized to the chromosome in 56 of the isolates while 9 isolates from farms A and B contained ermB on two similar-sized plasmid bands (12 to 16 kb). Pulsed-field gel electrophoresis revealed that the isolates were genetically diverse and represented a heterogeneous population of enterococci. This study suggests that although there was resistance to a greater number of enterococcal isolates on a farm where tylosin was used as a growth promotant, resistant enterococci also existed on a farm where no antimicrobial agents were used.

The effects of subtherapeutic antibiotic use in farm animals on the proliferation and persistence of antibiotic resistance among soil bacteria

“…There is considerable controversy regarding the necessity of such subtherapeutic antibiotic use compared to the threat it poses to human health (Ferber, 2003;Livermore, 2003;Arnold et al, 2004;Phillips et al, 2004). While it is agreed that subtherapeutic antibiotic use leads to an increase in antibiotic-resistant fecal bacteria in the animals (Levy, 1978;Aarestrup et al, 2001;Hayes et al, 2004;Jackson et al, 2004), the role of subtherapeutic antibiotic use in the global spread of antibiotic resistance remains ambiguous.…”

Distribution and persistence of fecal bacterial populations in liquid and dewatered sludge from a biological treatment plant

“…Vancomycinresistant enterococci (VRE) have been identified as an important cause of hospital-acquired infection (Goossens, 1998) and have been related to animal production (Aarestrup, 1995;Klare et al, 1995;Robredo et al, 1999;Stobbering et al, 1999;Teuber and Perreten, 2000). Enterococci isolates from animal and human origins have also been reported to carry erythromycin resistance genes (Jackson et al, 2004;Jensen et al, 1999). Consequently, resistance to these two antibiotics could be potentially transmitted through the bacterial population of wastewater and sludge, particularly in sewage treatment plants which have a high concentration of bacteria of distinct fecal origin.…”

Antimicrobial Resistance Arising from Food-Animal Productions and Its Mitigation

“…Although no precise quantitative relationship has been established, the accumulating body of data indicates a positive correlation between antimicrobial use and AMR development in food animals Mathew et al, 2007). As one example, in two farms where tylosin was used for growth promotion or treatment of diseases, 59% and 28%, respectively, of the E. coli isolates were resistant to tylosin, while only 2% of the E. coli isolated from an organic farm were resistant (Jackson et al, 2004). In another study, as much as 71% of the Enterococcus faecalis isolated from swine manure was resistant to tetracycline (Haack & Andrews, 2000).…”